Man - Lpl
Runway 2 at MAN is hardly 'useless'. The two runways are used simultaneously, but in segregated mode. The current declared capacity is 61 movements an hour and with additions to the taxiway system and an additional crossing point will take this to 70+ movements an hour.
Both runways are 3,000m in length and an available starter extension on 23L.
Linking MAN and LPL is a non-starter as a single complex. Providing improved rail access from Merseyside to Greater Manchester, and then to the Airport would be a much better option. There's £3bn of Transport Innovation Fund money on offer from the Government. But this depends on a Congestion Charge, and this is another subject for discussion ....